\[R \cdot \left(2 \cdot \tan^{-1}_* \frac{\sqrt{{\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)}}{\sqrt{1 - \left({\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right)}}\right)\]
R \cdot \left(2 \cdot \tan^{-1}_* \frac{\sqrt{{\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)}}{\sqrt{1 - \left({\left(\sin \left(\frac{\phi_1 - \phi_2}{2}\right)\right)}^{2} + \left(\left(\cos \phi_1 \cdot \cos \phi_2\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right) \cdot \sin \left(\frac{\lambda_1 - \lambda_2}{2}\right)\right)}}\right)double f(double R, double lambda1, double lambda2, double phi1, double phi2) {
double r505331 = R;
double r505332 = 2.0;
double r505333 = phi1;
double r505334 = phi2;
double r505335 = r505333 - r505334;
double r505336 = r505335 / r505332;
double r505337 = sin(r505336);
double r505338 = pow(r505337, r505332);
double r505339 = cos(r505333);
double r505340 = cos(r505334);
double r505341 = r505339 * r505340;
double r505342 = lambda1;
double r505343 = lambda2;
double r505344 = r505342 - r505343;
double r505345 = r505344 / r505332;
double r505346 = sin(r505345);
double r505347 = r505341 * r505346;
double r505348 = r505347 * r505346;
double r505349 = r505338 + r505348;
double r505350 = sqrt(r505349);
double r505351 = 1.0;
double r505352 = r505351 - r505349;
double r505353 = sqrt(r505352);
double r505354 = atan2(r505350, r505353);
double r505355 = r505332 * r505354;
double r505356 = r505331 * r505355;
return r505356;
}